It's always interesting trying to figure out what needs to go in, or come out, of a rulebook. Sure you need the rules, absolutely. Character generation needs to go in. Equipment lists are handy. Some information on the basic setting, particularly the kind of historical detail that isn't easy to find on your average wikipedia though general details need to go up there as well. That's easy enough.
But what about the supernatural aspects? How many entities should go into the creature compendium? How much advice should I give on creating your own? What kind of Game Warden advice is needed? What kind of Player Advice? What about paranormal societies, relics, and strange places? Is it more important to give examples or to provide tool kits? How many tool kits do people need? What kind of tool kits are they after? How much information is necessary?
These are the questions which boggle my mind when I consider the third section in the book. There's just so many options of what you *can* put into that section that it can make it hard to realise what you *should* put in there.
What about you guys? How much world material do you think should go into a core book?